3. 2 Ð English
Arrangement of the manual
This workshop manual can be used in two different
ways.
¥ To repair a speciÞc sub-assembly on a chainsaw.
¥ To dismantle and reassemble a complete chain-
saw.
Repairing a speciÞc sub-assembly
If a speciÞc sub-assembly on the chainsaw needs
to be repaired:
1. Look up the page referring to the relevant sub-
assembly.
2. Follow the instructions under the headings:
¥ Removal/Dismantling
¥ Cleaning and inspection
¥ ReÞtting/Reassembly
Dismantling and reassembling the entire chainsaw
If the entire chainsaw is to be dismantled, follow
the instructions under the heading ÒRemoval/Dis-
mantlingÓ.
Work through the manual and follow the instruc-
tions given in each section under the heading
ÒRemoval/DismantlingÓ.
Then follow all the ÒCleaning and inspectionÓ
instructions in each section.
Working from the back of the manual, follow all the
instructions under the headings ÒReÞtting/Reas-
semblyÓ in reverse order.
Each of the sections covering removal/dismant-
ling and reÞtting/reassembly include the relevant
lubrication instructions and bolt torques for each
stage of repair.
Construction and function
This chapter gives a simple description of the
chainsaw carburettor and its various parts.
Introduction
Troubleshooting
These pages describe the most common faults that
affect a chainsaw. They are divided into four dif-
ferent groups with the most likely faults described
Þrst.
Repair instructions
The section that describes how to repair the chain-
saw consists of detailed, step-by-step instructions.
It explains in detail the special tools, lubricants
and bolt torques that are needed when working on
each component.
This workshop manual covers the following
chainsaw models: 455
4. English Ð 3
General instructions
This workshop manual gives detailed instructions
on how to troubleshoot, repair and test a chainsaw.
This section also describes the various safety
precautions that should be taken when carrying out
repairs.
The workshop manual has been written for person-
nel who are assumed to have general experience
of repairing and servicing chainsaws.
Workshops where chainsaws are repaired must be
equipped with safety equipment that meets local
regulations.
No-one should carry out repairs on a chainsaw
until they have read and understood the contents
of this workshop manual.
Chainsaws are type-approved to meet the relevant
safety legislation, but this only applies when the
saw is Þtted with the cutting equipment speciÞed
in the userÕs manual. The Þtting of any other
equipment, or of accessories or parts that are not
approved by Jonsered, could mean that the saw
no longer meets these safety requirements and
the person who carried out the work may be held
responsible for its non-conformance.
In this workshop manual the following boxes
indicate where caution should be taken.
Special instructions
The fuel that is used in a chainsaw poses the fol-
lowing hazards:
¥ The fuel and its fumes are toxic.
¥ May cause irritation to skin or eyes.
¥ May cause breathing difÞculties.
¥ Highly ßammable.
When using compressed air the air jet should
never be pointed at the body. Air can be forced into
the bloodstream and cause fatal injury.
Wear ear protection when testing saws.
After testing a saw do not touch the silencer until
it has cooled down. The silencer gets very hot and
you may burn yourself. Wear protective gloves
when working on the silencer.
The guide bar, chain and clutch cover (chain
brake) must be Þtted before the saw is started. If
not, the clutch may come loose and cause injury.
Poor chain lubrication can result in failure of the
chain, which could cause serious or fatal injury.
Take care to ensure that the spring inside the
starter assembly does not ßy out and cause injury.
Wear eye protection. If the spring is under
compression when the pulley is removed it could
ßy out and cause injury.
Before removing the tensioning spring from the
chain brake, ensure that the brake is in the on
position, otherwise the spring may ßy out and
cause injury.
After completing the repair the chain brake must be
tested, see ÒChain brake Ð reassembly Operating
testÓ.
Always consider the Þre risk. A chainsaw can
produce sparks that could start a Þre.
Inspect the chain catcher and replace it if it is
damaged.
WARNING!
The warningtext warns ofthe risk
ofpersonal injuryifthe instruc-
tions are not followed.
NOTE!
The warningtext warns ofthe riskof
material damage ifthe instructions are
not followed.
Safetyregulations
7. 6 Ð English
Displacement Cylinder bore Stroke Max power/speed
cm
3
/cubic inches ¯ mm/¯ inches mm/inches kW/hp/rpm
455: 55,5 / 3,38 47 / 1,85" 32 / 1,28" 2,5 / 3,4 / 9 000
Spark plug gap Ignition system Air gap Carburettor type
mm/inches mm/inches
455: 0,5 / 0,02" SEM CD 0,3 / 0,012" Walbro WTA 29
Effective cutting length Chain speed at Chain pitch Drive link
cm/inches max power Ð revs mm/inches mm/inches
m/s Ð rpm
455: 31-50 / 13"-20" 17,3 / 9 000 9,52 / 3/8 1,3 / 0,050" - 1,5 / 0,058"
8,25 / 0,325"
Technical data
8. English Ð 7
Technical data
Idling speed Engagement speed Max. speed Spark plug
rpm rpm rpm
455: 2 700 3 800 13 500 NGK BPMR 7A
Champion RCJ 7Y
Fuel tank capacity Oil pump capacity at Oil tank capacity Automatic oil pump
Litres/US pints 8,500 rpm, Litres/US pints
ml/min
455: 0,44 / 0,93 9 0,32 / 0,68 Yes
Weight without Weight with
bar and chain bar and chain
kg / lbs kg / lbs
455: 5,8 / 12,8 6,2 / 13,6
9. 8 Ð English
Carburettor
WARNING!
The fuel used in the chainsaw has
the following hazardous properties:
1. The ßuid and its fumes are poi-
sonous.
2. Can cause skin irritation.
3. Is highly inßammable.
Carburettor
Description
The drawings accompanying this description do
not correspond with the carburettor on the chain-
saw. They only show the principle for the design
and function.
Design
The carburettor is based on three sub-systems:
¥ The metering unit, A.
¥ The mixing venturi, B.
¥ The pump unit, C.
The jets and the fuelÕs control functions are located
in the metering unit (A). Here the correct quantity
of fuel is adjusted for the actual speed and power
output.
A
B
C
The mixing venturi (B) houses the choke, throttle
valve and diffuser jets. Here air is mixed with the
fuel to give a fuel/air mixture that can be ignited by
the ignition spark.
In the pump unit (C), fuel is pumped from the fuel
tank to the metering unit. One side of the pump di-
aphragm is connected to the crankcase and pulses
in time with the pressure changes in the crankcase.
The other side of the diaphragm pumps the fuel.
10. English Ð 9
Carburettor
Function
The carburettor operates differently in the following
modes:
¥ Cold start mode
¥ Idling mode
¥ Part throttle mode
¥ Full throttle mode
In the cold start mode (see Þgure below) the choke
valve (H) is fully closed. This increases the vacuum
in the carburettor so that fuel is sucked more easily
from all the diffuser jets (D, E and F). The throttle
valve (I) is partly open. Extra air inlet (J) is closed.
I
H
D F
E
J
I
D
J
I
J
D F
E
D F
E
In the idling mode the throttle valve (I and J) is
closed.
Air is sucked in through an aperture in the throttle
valve and a small amount of fuel is supplied th-
rough the diffuser jet (D).
In the part throttle mode the throttle valve (I) is
partially open. Fuel is supplied through the diffuser
jets (D and E).
In full throttle mode all valves are open and fuel is
supplied through all diffuser jets (D, E, F and G).
Extra air inlet (J) is also fully opened.
11. 10 Ð English
Carburettor
Carburettor Ð removal
1
Remove the cylinder cover and air Þlter. Discon-
nect the leads from the stop switch and the fuel
hoses from the carburettor. Pull out and lift up the
strip (A), see Þgure.
2
NOTE!
Do not use knurled pliers to disconnect or
reconnect the fuel hose. This could damage
the hose and lead to leakage or fracture.
Loosen the screws (4) on the carburettor. Lift the
carburettor out of the carburettor compartment.
5
Remove the cover (A) over the metering unit and
carefully remove the metering diaphragm (B) and
gasket. See Þgure below.
6
Remove the screw (E) and take out the needle
valve (D) with lever (C), spindle and spring. See
Þgure below.
Dismantle the throttle actuator rod by pulling out
and lifting up C from its seating. First remove the
throttle actuator rod from the lever and then from
the handle.
3
4
A
C
B
B
Loosen the carburettorÕs rubber mounting (B).
7
Remove the cover (J) over the pump unit and
carefully remove the gasket (I) and pump diaphragm
(G). See Þgure below.
A
B
C
D
E
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13. English Ð 11
WARNING!
Neverdirectthecompressedair
jettowardsthebody.Aircanpe-
netrateintothebloodcirculation,
whichmeansmortaldanger.
WARNING!
Fuelhasthefollowinghazardous
properties:
1.Theßuidanditsfumesarepoi-
sonous.
2.Cancauseskinirritation.
3.Ishighlyinßammable.
Cleaningandinspection
See Þgures on previous page and check the fol-
lowing:
1
That gaskets, pump and control diaphragms are
undamaged.
2
That there is no play on the throttle and choke valve
shafts.
3
The needle valves and lever are not worn at C and D
in Þgure on previous page.
4
The fuel Þlter is undamaged.
5
The tips of the high and low speed screws are not
damaged.
8
Use a needle or the like to carefully remove the
fuel Þlter (F). See Þgure below.
9
Remove caps with the high and low speed screws.
See Þgure below.
10
If necessary, remove the throttle and choke valves
and remove the spindles together with levers and
springs. See Þgure below.
6
The intake manifold is undamaged.
7
The carburettor has an extra air shutter connected
in parallel with the ordinary throttle valve. The
valve housing with axle is secured in the carburet-
tor using two screws.
Carburettor
Clean all units in clean petrol.
Use compressed air to dry the petrol on the com-
ponents. Direct the air through all channels in the
carburettor housing and make sure that they are
not blocked.
F
G
I
J
14. 12 Ð English
Assembly
Where no Þgure is referred to, see Þgure on the
previous page.
Maintain a high level of cleanliness when assem-
bling the carburettor. The slightest contamination
can result in running problems.
1
If the throttle and choke valves, together with
levers and springs were removed, they should be
reÞtted. Lubricate the spindle bearings with light oil.
2
Fit the high and low speed screws and springs.
Note! Do not fully tighten the screws. This will
damage the seats and needle tips.
3
Fit the fuel Þlter (F) by using the handle of a small
screwdriver. See Þgure below.
4
Fit the pump diaphragmas (G and H), gasket (I)
and cover (J) on the pump unit. See Þgure below.
F
G
I
J
C
D
E
7
Fit the control diaphragm (B) with gasket and cover
(A) on the metering unit. See Þgure below.
A
B
5
Fit the needle valve (D) with lever (C), spindle and
spring and tighten the screw (E). Fit welch plug (K).
See Þgure below.
6
Check with a ruler or the like that the lever is level
1.65 mm below plane. See Þgure below. If neces-
sary, the lever can be bent slightly.
Carburettor
8
Fit the axle on the air shutter (L) and connect the
throttle actuator rod (N) in parallel with the ordinary
throttle valve. The valve housing (P) is secured in
the carburettor using two screws.
